Cement paste in which water is added to cement, mortar in which sand as fine aggregate is mixed into the cement paste, and concrete having fluidity improved by a dispersant, in which gravel as coarse aggregate is further mixed into the mortar have been used in great quantities for various structural materials and the like. In such concrete, concrete products (precast concrete) have been in increasing demand mainly in Europe and America. Concrete products are made by pouring concrete into a formwork in factories, and concrete members thus made are carried to a building site and constructed. In a method of producing such concrete products, deforming from a formwork in early stages is required for the purpose of improving productivity in factories, and an usual dispersant causes a high degree of hardening-retardation and needs a long time until deforming. Steam curing is generally performed in factories, also in which case increasing the turnover of a formwork and improving productivity is required. Standard processes of steam curing are as follows. That is, concrete is poured into a formwork and compacted to thereafter stand as pre-curing at ordinary temperature for approximately 2 to 4 hours. Subsequently, vapor starts to be ventilated and the concrete is heated up by a heating-up temperature of 15 to 20° C./hour (in general, 20° C./hour or less). Typically, after reacting a curing temperature of approximately 50 to 80° C., isothermal curing is performed while maintaining the temperature for 2 to 4 hours to thereafter stop the ventilation of vapor, and the curing ends through a slow cooling period by natural standing to cool. Deforming from the formwork is performed during this slow cooling period to divert the formwork to next producing cycle. Also, a manner such as to cover the periphery of a formwork with a heal insulator (an isolating material) is occasionally adopted as a method for increasing the turnover of a formwork except steam curing. This allows time for deforming to be shortened by utilizing self-heat of hydration of cement to promptly raise the temperature in the system.
Further, an improvement in durability and strength of concrete buildings have been greatly required in the recent concrete industry, and a reduction in the unit water content has been an important problem for achieving this improvement. In addition, mortar and concrete is hardened by the progress with time of hydration reaction between cement and water, so that slump loss is generally inevitable, which is a phenomenon of the deterioration of fluidity with time passing after adding water. Accordingly, a dispersant has been required, which allows the dispersing ability of cement to be held and is suitable for producing a concrete product.
The following precedent technical document is referred to for a conventional polycarboxylic acid cement dispersant.
Japanese Kokai Publication Hei-08-12396 discloses a copolymer and the like obtained by polymerizing methoxypolyethylene glycol acrylate (the molar number of addition of the ethylene oxides (EO) is 75) and sodium acrylate, with respect to a concrete admixture using polyalkylene glycol ester monomer, wherein the terminal group is a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms and the molar number of addition of the oxyalkylene groups is 50 to 100. However, there was a room for contrivance in order to suitably make it possible to use such concrete admixture for concrete products and the like, by further improving hardening-retardation and further improving strength in early stages.
Japanese Kokai Publication Hei-08-225352 discloses a concrete admixture using polyalkylene glycol monoester monomer, wherein the terminal group is a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms and the molar number of addition of the oxyalkylene groups is 100 to 110. Japanese Kokai Publication Hei-07-223852 discloses a concrete admixture containing a copolymer obtained by polymerizing methanol EO/acrylic acid monoester (the molar number of addition of EO is 220) and acrylic acid in Examples, with respect to a concrete admixture using polyalkylene glycol monoester monomer, wherein the terminal group is a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms and the molar number of addition of the oxyalkylene group is 110 to 300. However, these concrete admixtures are not considered to be suitably used for concrete products; therefore, there was a room for contrivance in order to make it possible to use such concrete admixtures preferably for concrete products and the like, by improving strength in early stages with a high dispersing ability obtained.
Japanese Kokai Publication Hei-08-12399 discloses an admixture composition for concrete products using polyalkylene glycol monoester monomer, wherein the terminal group is a hydrogen atom or an alkyl group containing 1 to 3 carbon atoms and the molar number of addition of the oxyalkylene groups is 110 to 300. However, this admixture composition for concrete products is used for manufacturing concrete products compacted by a vibrator and centrifugal force, and is intended for shortening molding time by reducing air voids on the surface of the products and improving the compacting properties of concrete. Therefore, there was a room for contrivance in order to suitably make it possible to use such admixture composition for concrete products and the like, by improving hardening-retardation and further improving strength in early stages, for the purpose of improving productivity in factories.
Japanese Kokai Publication Hei-11-106248 discloses a cement admixture containing a copolymer of 1-butoxypolyethylene monomethacrylate (the molar number of addition of the ethylene oxides is 75 to 130) and methacrylic acid in Examples, with respect to a cement admixture using polyalkylene glycol monoester monomer, wherein the terminal group is an alkyl group containing 2 to 5 carbon atoms and the molar number of addition of the oxyalkylene groups is not less than 30. Japanese Kokai Publication Hei-09-241056 discloses a concrete admixture using polyalkylene glycol monoester monomer, wherein the terminal group is an alkyl group containing 6 to 18 carbon atoms and the molar number of addition of the oxyalkylene groups is 2 to 300. However, also in such concrete admixture, there was a room for contrivance in order to increase in the turnover of a formwork by deforming in early stages in the case of using for concrete products, by further improving hydrophilicity and improving hardening-retardation.
Furthermore, the following precedent technical document is referred to for a conventional cement dispersant using a sulfonic acid monomer.
Japanese Kokai Publication Sho-62-119147 discloses a cement dispersant using a copolymer of sodium 2-sulfoethyl acrylate, sodium acrylate and methoxy polyethylene glycol monoacrylate (the molar number of addition of the ethylene oxides is 10) in Examples, with respect to a cement dispersant using sulfonic acid monomer as a necessary component. However, this cement dispersant is intended for securing a stable workability by improving the slump loss preventing ability, for which a copolymer having a high content of 2-sulfoethyl acrylate sodium is used. In view of structure and content of a sulfonic group-containing monomer, therefore, there was a room for contrivance in order to suitably make it possible to use such dispersant for manufacturing concrete products and the like, by improving dispersing ability and strength in early stages for the purpose of improving productivity in factories.
Japanese Kokai Publication Hei-07-172891 discloses a cement dispersant using a copolymer of vinyl compounds containing a sulfonic acid group, sodium (meth)acrylate, and methoxy polyethylene glycol mono(meth)acrylate (the molar number of addition of the ethylene oxides is 4 to 23) in Examples, with respect to a cement dispersant using a copolymer of vinyl compounds having polyoxyalkylene chain and vinyl compounds containing a sulfonic acid group. However, this cement dispersant has a high content of sulfonic acid in a copolymer; therefore, there was a room for contrivance in order to increase in the turnover of a formwork by deforming in early stages in the case of using for producing concrete products, by further improving dispersing ability and strength in early stages.
Japanese Kokai Publication Hei-11-79811 discloses a cement dispersant using a copolymer of a sulfonic acid group-containing monomer, (meth)acrylic acid, and esterified compound (the molar number of addition of the ethylene oxides is 23 to 350) obtained by esterification of polyethylene glycol containing lower alkyl group at one end and (meth) acrylic acid, in Examples, with respect to a cement dispersant using a vinyl copolymer containing a long-chain oxyalkylene group and a specific monomer. However, this cement dispersant is intended for improving workability by achieving a low viscosity of concrete. In order to improve productivity in factories, therefore, there was a room for contrivance in order to suitably make it possible to use such dispersant for concrete products and the like, by improving hardening-retardation and further improving strength in early stages.